ad_group_cpa_cap_preview

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds genuinely new context: Apple deprecated it and it will not silently convert to a new bid strategy, which changes how an agent should interpret the preview result.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Is the description appropriately sized, front-loaded, and free of redundancy?

A single compact sentence that front-loads the most important fact (deprecation) and packs the compatibility caveat into the same clause. Nothing is redundant.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With a full schema, an output schema, and rich annotations, the description only needs to add the deprecation and no-conversion semantics, which it does. Slightly more detail on what the preview returns or when to prefer the modern alternative would complete it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and every parameter (amount, currency, profile, adAccountId, adGroupId) is documented in the schema. The description adds no parameter-level guidance such as currency/amount units or ID format, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Does the description clearly state what the tool does and how it differs from similar tools?

Names a specific verb (preview) and resource (legacy ad-group CPA cap update), which is more specific than the sibling ad_group_update_preview. It does not explicitly contrast with ad_group_bid_preview or target_cpa_recommendation_apply_preview, so an agent must still infer the boundary, keeping it below a 5.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Does the description explain when to use this tool, when not to, or what alternatives exist?

The deprecation notice and 'retained for compatibility' hint that new work should avoid this tool, but there is no explicit 'use X instead' routing to the modern CPA/bid strategy preview tools. Usage is implied rather than stated.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.